Cosmetic sticks are well known as delivery systems for deodorants, antiperspirants, astringents and medicaments. Sticks are advantageous over aerosols in that they obviate the need for a fluorocarbon propellant which may cause environmental damage.
Conventionally, transparent cosmetic compositions have been made using a soap/alcohol formulation. Such compositions have been formed as gel sticks which act as vehicles for delivery of active ingredients, such as perfumes and bactericides. Propylene glycol or ethanol are commonly used as solvents.
Sticks based on soap (e.g. sodium stearate), propylene glycol and ethanol are desirable in producing a pleasant cooling effect on the skin but it is found that to obtain moderate degrees of cooling, transparency is lost. This is exemplified in patent EP 107 330 (Procter & Gamble) which describes a deodorant gel stick containing hydro-alcoholic soluble emollients. The composition contains less than 12.5% of a short-chain monohydric alcohol, e.g. ethanol.
U.S. Pat. No. 4,268,498 (Revlon) describes clear cosmetic sticks comprising a soap/alcohol gel base. It proposes the use of polyoxyethylene-glucose fatty acid esters and of ethers of long-chain alcohols to replace short-chain monohydric alcohols. In this case the term "clear stick" is not strictly accurate and refers to a translucent as well as transparent stick.
We have now found that the problems of combining transparency with a level of alcohol which will give a stable transparent soap-based stick with desirable cooling effect may be overcome by using glycerol as the humectant/solvent. This results in a stable, transparent stick. Other solvents may also be present, such as propylene glycol and water. Varying the content of these other solvents may optimise the sensory feel of the product.